Method and apparatus for identifying documents

ABSTRACT

A method and apparatus for identifying a document ( 55 ). The method comprises exposing the document ( 55 ), such as a banknote, to infrared radiation; detecting infrared radiation reflected from a plurality of regions of the document ( 55 ) to generate at least one test pattern; determining if the or each test pattern satisfies a predetermined relationship with a predetermined pattern or patterns corresponding to a known document; and, if the predetermined relationship is satisfied, identifying the document ( 55 ) as being the same as the known document.

The invention relates to a method and apparatus for identifying adocument, typically a document of value such as a banknote, travellerscheque, postal order and the like.

A variety of security document handling equipment has been developedover many years. Typical examples are sorters, counters, validators,dispensers, acceptors and recirculators. Often this equipment needs toidentify the documents (e.g. banknote denomination) and this has oftenbeen achieved by detecting the size of banknotes (where differentdenominations have different sizes) and by detecting visible lightpatterns on the documents for comparison with predetermined references,as in U.S. Pat. No. 4,542,829.

In addition, checks are also made that the documents are genuine andthis is commonly achieved by monitoring the UV and IR characteristics ofthe documents, typically their reflective and/or transmissive responseto such irradiation. Examples are described in U.S. Pat. No. 4,127,328,EP-A-0083062, EP-A-0679279, U.S. Pat. No. 4,296,326 and EP-A-0807904.

In large scale document handling equipment, sophisticated detectors canbe incorporated for determining identity and authenticity as well asother properties such as degree of soil and the like. Recently, a numberof more compact banknote counters have been developed which are able todetermine denomination and authenticity and which transport thebanknotes either to a single output hopper or to a limited number ofoutput hoppers, for example just two or three. Examples include the DeLa Rue 2700 and 2800 machines.

There is a need to reduce the size and complexity of this equipment.

In accordance with a first aspect of the present invention, a method ofidentifying a document comprises exposing the document to infraredradiation; detecting infrared radiation reflected from or transmittedthrough a plurality of regions of the document to generate at least onetest pattern; determining if the or each test pattern satisfies apredetermined relationship with a predetermined pattern or patternscorresponding to a known document; and, if the predeterminedrelationship is satisfied, identifying the document as being the same asthe known document.

In accordance with a second aspect of the present invention, documenthandling apparatus comprises an infrared inspection station; a transportsystem for transporting documents past the inspection station, theinspection station comprising an infrared radiation emitter and aninfrared radiation receiver for detecting infrared radiation reflectedfrom or transmitted through a document; and a control system coupled tothe transport system and the infrared inspection station to generate atleast one test pattern from the infrared radiation reflected from ortransmitted through a plurality of regions of the document, to determineif the or each test pattern satisfies a predetermined relationship withthe predetermined pattern or patterns corresponding to a known document,and, if the relationship is satisfied, to identify the document as beingthe same as the known document, and thereafter to control the transportsystem accordingly.

In this new approach, we have realised that it is possible with certaindocuments such as banknotes, for example US and Spanish currency, todetermine identification by reference to reflected or transmittedinfra-red radiation properties of the documents. In this way, it ispossible not only to determine identification but also authenticityusing the same infra-red response or at least the same infra-redinspection station and thus reduce the size and complexity of theapparatus. Typically the same information will be used for bothidentification and authenticity but in some cases i.r. reflection couldbe used for identification and i.r. transmission for authenticity orvice versa, or i.r. information from different parts of the documentcould be used for identification and authenticity respectively.

Although in most cases, the “identity” of the document refers to itsdenomination or value in the case of banknotes, it can include also orinstead orientation or issue.

In addition, the invention enables a new form of non-contact detectionto be introduced into the document counting product environment thatprovides enhanced authentication that was previously only found in themuch higher cost document sorting arena. The non-contact nature of thedetector provides the advantage that document guiding constraints areminimized and the range of documents that can be processed is maximized.

Although a primary advantage of the invention is that the infra-redresponse of the document can be used to determine identification, themethod could be used in conjunction with a conventional identificationdetection system such as a visible pattern recognition system to produceadditional confirmation of the identity.

The regions which are inspected may be arranged in an irregular orregular array and could be on one or both sides of the document. In thepreferred approach, the whole of at least one side of a document isinspected.

The intensity information obtained can be processed in any conventionalway. For example, the pattern may be compared using conventionalcomparison algorithms with one or a number of predetermined patternscorresponding to different identities, issues and/or orientations ofdocuments. Alternatively, the test pattern could be applied to apreviously generated neural network which has been trained with therange of genuine documents which are to be identified.

The method can be implemented in a variety of document handlingapparatus but is particularly suited for simple document counters havingone or a limited number of output locations.

In one example, the infrared inspection station comprises two sets ofinfrared emitters and detectors arranged on opposite sides of thetransport path so as to view opposite sides of the documents. Thisenables a more accurate determination of identity to be determined sincetwo patterns will be generated from one document. Conveniently, thearrays are offset from one another in the transport direction so as tominimize interference between the two. This also enables each array tobe arranged opposite a black reference surface.

Some examples of methods and apparatus according to the invention willnow be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram showing the primary transport componentsof a first example of a banknote counter;

FIG. 2 is a schematic block diagram of an infrared head;

FIG. 3 illustrates schematically the appearance of the relationshipbetween an infra-red head and a banknote;

FIG. 4 is a block diagram of the control system;

FIG. 5 is a flow diagram illustrating operation of the system;

FIG. 6 is a side view of part of a second example of a banknote counter;and,

FIG. 7 is a view similar to FIG. 1 but of a further example.

FIG. 1 illustrates a banknote counter 100 having an input hopper 2mounted beneath an inlet opening 3 in an enclosure 1 which comprisesupper and lower parts 1 a, 1 b normally screwed together. Containedwithin the enclosure 1 is an internal chassis assembly (not shown forclarity) which itself has side members between which the sheet feedingand transport components to be described herein, are mounted. Twoconventional feed wheels 5 are non-rotatably mounted on a shaft 7, whichis rotatably mounted to the chassis assembly, and have radiallyoutwardly projecting bosses 6 which, as the feed wheels rotate,periodically protrude through slots in the base of the hopper 2.

A pair of stripper wheels 15 are non-rotatably mounted on a drive shaft16 which is rotatably mounted in the chassis assembly. Each stripperwheel 15 has an insert 17 of rubber in its peripheral surface. Shaft 16is driven clockwise by a motor 200 (FIG. 4) to feed notes individuallyfrom the bottom of a stack of notes placed in the hopper 2.

Transversely in alignment with, and driven from the circumferentialperipheral surface of the stripper wheels 15, are pressure rollers 30which are rotatably mounted on shafts 31 spring-biased towards thestripper wheels 15. Downstream of the wheels 15 is a pair of transportrollers 19 non-rotatably mounted on a shaft 20 rotatably mounted in thechassis assembly. Each roller 19 has a cylindrical form with a constantradius along its axis. Shaft 20 is driven clockwise from a second motor(not shown) to transport the note in the transport arrangement, inconjunction with pairs of pinch rollers 21,23 into stacking wheels 27and hence output hopper 105. Pinch rollers 21, rotatably mounted onshafts 22 spring based towards the transport rollers 19, transverselyalign with rollers 19 and are driven by the peripheral surface of therollers 19. The rollers 23, rotatably mounted on shafts 24 are inalignment with the transport rollers 19, and are essentially caused torotate by the note passing between the adjacent peripheral surfaces ofthe rollers 19 and 23.

Situated between the pressure rollers 30 and pinch rollers 21 areseparator roller pair 25, non-rotatably mounted on shaft 26 adjustablyfixed to a top moulding assembly 32, having a circumferential peripheralsurface which is nominally in alignment with the peripheralcircumferential surface of, but transversely separated from, thestripper wheels 15.

Also forming part of the top moulding assembly 32, is a curved guidesurface 8 extending partly around the circumference of the rollers 15,19 which, when the top moulding is lifted allows the operator access tothe note feed and transport path so that a note jam can be cleared. Asurface 37 provides note guiding from the end of the curved guidesurface 8 to the conventional stacking wheels 27.

The drive shaft 16 is continuously driven, and this, via a belt andpulley arrangement from shaft 16, causes the auxiliary drive shaft 7rotating the feed wheel 5 also to be driven. Drive shaft 20, rotatingthe transport rollers 19, is driven by the other drive motor. A furtherpulley and belt arrangement (not shown) between shaft 20 and shaft 28,on which the stacking wheels 27 are non-rotatably mounted, provides thedrive to the stacking wheels 27.

The guide plate 8 extends as a continuation of the base of the hopper 2towards the nips formed between the transport rollers 19 and the rollers23.

An infra-red head 50 is mounted downstream of the rollers 21 andincludes a linear array of infra-red emitting diodes 51 (FIG. 2) and alinear array of, typically 144, photodiodes 52. In particular, thelinear array 51 typically comprises 92 LEDs extending collectively alength of about 9″ (23 cms) while the linear array of photodiodes 52extends a comparable length (FIG. 3). The LEDs are preferably ForgeEuropa FT-N102W and the photodiodes are preferably the Photodiode Array#180381-8 (available from UDT). The head 50 is located opposite to areference black surface forming part of the note guide as illustrated at53. It will be appreciated that the head 50 and surface 53 are laterallyoffset from the rollers 19. As a banknote 55 is conveyed by thetransport system, it will pass beneath the head 50 and be irradiated bythe light emitting diodes 51 with infra-red radiation. This radiation isreflected by the banknote in dependence upon the materials on or in thebanknote, the reflected radiation being detected by the photodiodes 52.The output signals from the photodiodes 52 are regularly sampled so asto generate a set of intensity values for each region or pixel of thebanknote 55, this information being stored in a memory 60 (FIG. 4).

The infra-red head 50 is connected to a microprocessor 65 which is alsoconnected to the memory 60. This is described in more detail inWO-A-00/26861 incorporated herein by reference and so will not bedescribed in detail. The microprocessor 65 is programmed to identify thedenomination of the banknote and also its authenticity. In one example,the denomination and authenticity are determined separately. Forexample, certain regions of the banknote will be reviewed for thepurposes of denomination determination while other regions will bereviewed for purposes of authenticity. However, in other applications,particularly if the whole banknote is considered, then a single processcan be used to establish both denomination and authenticity.

As far as denomination is concerned, the processor 65 compares all orpart of the test pattern stored in the memory 60 with a plurality ofreference or prestored patterns in a memory 70. These prestored patternswill have been generated in any conventional manner from a set ofgenuine banknotes.

Thus, as set out in FIG. 5, once the infra-red test pattern has beenobtained and stored (step 80), it is compared by the processor 65 witheach prestored pattern (step 85). These prestored patterns may define asingle banknote in one or more of its possible orientations or aplurality of banknotes also in one or more of their orientations. Theprocessor 65 then selects the most similar prestored pattern (step 90)and determines whether the degree of similarity exceeds a firstthreshold (step 95). If it does not, then the system determines that thebanknote is unrecognizable (step 110). Otherwise, the processor 65determines whether the difference between the degrees of similarity ofthe test pattern with the two most similar prestored patterns exceeds asecond threshold (step 120) so as to establish whether or not there is aclear match. If there is then the banknote is identified with the mostsimilar prestored pattern (step 125) while otherwise the banknote isconsidered to be not identified.

The pattern matching technique used in step 85 can be of anyconventional type, a preferred approach being described inWO-A-00/26861. Other examples are described in U.S. Pat. No. 4,179,685and EP-A-0883094.

As mentioned above, the processor 65 could carry out a separateauthenticity determination by looking at a particular region of thebanknote to see whether the infra-red reflectance satisfies apredetermined condition or alternatively this could be inherent in thepattern recognition process carried out to determine denomination. Ineither event, if the processor 65 is satisfied that the banknote isauthentic and its denomination has been identified it will then controlthe subsequent processing and handling of the banknote. In this example,the banknote will be allowed to continue on to the output hopper 105 andfurther banknotes will be fed from the input hopper 2.

If the processor 65 determines that the banknote is not authentic orcannot be identified then the motor 200 is stopped to prevent furtherbanknotes from being fed to the output hopper and a suitable errormessage will be displayed allowing the operator to remove the suspectbanknote.

In the example just described, a single IR head 50 was provided. FIG. 6illustrates part of the transport apparatus of a second example in whichbanknotes are fed into a nip between a pair of pinch rollers 204,205 andare guided by respective guide plates 210,215 through an inspectionstation 220 comprising a pair of infra-red heads 50,225 each locatedopposite a black reference surface 230,235 respectively defined by theguides 210,215 respectively. The head 225 has a similar construction tothe head 50. The banknotes pass on through a nip formed by pinch rollers240,245 and past an optical head 250. FIG. 4 illustrates the connectionof these components to the processor 65, those components shown in FIG.6 but not used in the FIG. 1 example being defined by dashed lines.

In the FIG. 6 example, infra-red images from both sides of the banknotewill be obtained and respective comparisons with prestored patterns inthe memory 70 will be carried out. Each of these comparisons will leadto a probability of the banknote being identified with a particularprestored pattern. In addition, the optical head 250 enables a visualimage of the banknote to be obtained and this can again be compared withprestored reference images to yield a probability that the banknote is aparticular denomination. These probabilities can then be combined by theprocessor 65 to yield a final probability enabling it to make a finaldecision on the banknote's identity depending upon the resultantprobability.

The apparatus shown in FIG. 6 could be incorporated into the FIG. 1machine.

Alternatively, the detection systems described with reference to FIGS. 1and 6 could be utilised in other banknote handling machines,particularly a two output pocket machine, the processor 65 being coupledto a diverter 255 which is operated in accordance with the decisionreached by the processor to guide a banknote to one or other of theoutput pockets.

In the case of a transmissive system, the detector(s) would be locatedon the opposite side of the transport from the corresponding emitter(s)in a similar way to the arrangement shown in WO-A-00/26861.

The counter 100 shown in FIG. 1 has a single output hopper 105. Theinvention is also applicable, however, to counters/sorters havingmultiple output hoppers and FIG. 7 illustrates such an example with twooutput hoppers. The FIG. 7 counter 300 has an input hopper 401 having abase 402 with an aperture 403, through which a high friction portion 404of a nudger wheel 405 can project. The base 402 optionally has a secondaperture 406 in alignment with a barcode reader 407 for reading data onnote separators. Bank notes are supported in a stack on, the base 402against a front wall 426, and are fed intermittently by rotation of thenudger roller 405 into a nip 408, between a high friction feed roller409 and a separate, counter rotating roller 410. The nudger 405 androller 409 are driven by a motor 200 (not shown). The documents passthrough pinch rollers 411,412 into a pattern detection region 413 inwhich a sensor of a transmission pattern recognition system 414A,414B(414B indicating an infra-red radiation source similar to the array 51and 414A indicating an array of photodiodes similar to the array 52)scans the bank note as it is fed and passes information back to amicroprocessor of the system 414A (not shown). Each bank note is thenfed through pinch rollers 416,417 onto a drive belt 418 which conveysthe bank note around various rollers 419 to a diverter 420. At least oneof the rollers is driven by a motor (not shown). The position of thediverter 420 is controlled by the microprocessor of the system 414A, sothat bank notes are guided either towards an output pocket 421, wherethey are stacked using a rotating stacking wheel 422 in a conventionalmanner, or to a reject bin 423.

As can be seen, the bank notes are stacked on the base 402 and are urgedforward against the front wall 426. A small gap 427 is provided at thebase of the front wall, through which individual bank notes andseparators can be nudged.

The pattern recognition system 414A,414B operates on the detected imagedata in an exactly similar way to the pattern recognition system of theprevious example, for example as described in WO-A-00/26861. In thiscase, however, instead of stopping the transport when an unsatisfactorycondition is determined such as a double note feed or the like, thediverter 420 is operated so that the unacceptable notes are fed to thereject bin 43.

In another alternative (not shown), in any of these examples bi-colourLEDs or sets of alternately activatable red and i.r. LEDs could be usedto obtain visible and i.r. pattern data for subsequent processing bysuitably switching activation of the LEDs as the note is scanned.

In all the examples, notes are typically processed at transport speedsin excess of 800 notes per minute, usually in excess of 1200 notes perminute.

1. A method of identifying a document, the method comprising exposing the document to infrared radiation; detecting infrared radiation reflected from or transmitted through a plurality of regions of the document to generate at least one test pattern; determining if the or each test pattern satisfies a predetermined relationship with a predetermined pattern or patterns corresponding to a known document; and, if the predetermined relationship is satisfied, identifying the document as being the same as the known document.
 2. A method according to claim 1, wherein the regions are arranged in a regular array.
 3. A method according to claim 1, wherein the regions are located on both sides of the document.
 4. A method according to claim 1, wherein the regions are arranged in one or more two dimensional arrays.
 5. A method according to claim 4, wherein the regions extend over substantially the whole of at least one side of the document.
 6. A method according to claim 1, wherein the step of determining if the or each test pattern satisfies a predetermined relationship comprises determining the relationship of the test pattern(s) with a plurality of predetermined patterns corresponding to different documents and/or orientations of documents, and identifying the document under test in accordance with the determined relationship.
 7. A method according to claim 1, wherein the step of determining the predetermined relationship includes determining whether the degree of similarity between the test pattern(s) and the or each predetermined pattern corresponding to a known document exceeds a first threshold.
 8. A method according to claim 7, wherein the step of determining if the or each test pattern satisfies a predetermined relationship comprises determining the relationship of the test pattern(s) with a plurality of predetermined patterns corresponding to different documents and/or orientations of documents, and identifying the document under test in accordance with the determined relationship, and wherein determining the predetermined relationship further comprises determining the two predetermined patterns which are most similar to the test pattern, and only identifying the document if the difference between the degrees of similarity to the two most similar predetermined patterns exceeds a second threshold.
 9. A method according to claim 1, wherein the document comprises a banknote.
 10. A method according to claim 9, wherein the banknote is US currency.
 11. A method of handling documents, the method comprising: transporting the documents past an infrared inspection station; performing an identification method according to claim 1 at the inspection station; and controlling the further transport of the documents in accordance with the outcome of the identification method.
 12. A method according to claim 11, further comprising transporting each document to an appropriate one of a plurality of output locations depending upon the outcome of the inspection method.
 13. A method according to claim 12, further comprising stopping the transport of the documents if a document is not identified.
 14. Document handling apparatus comprising an infrared inspection station; a transport system for transporting documents past the inspection station, the inspection station comprising an infrared radiation emitter and an infrared radiation receiver for detecting infrared radiation reflected from or transmitted through a document; and a control system coupled to the transport system and the infrared inspection station to generate at least one test pattern from the infrared radiation reflected from or transmitted through a plurality of regions of the document, to determine if the or each test pattern satisfies a predetermined relationship with the predetermined pattern or patterns corresponding to a known document, and, if the relationship is satisfied, to identify the document as being the same as the known document, and thereafter to control the transport system accordingly.
 15. Apparatus according to claim 14, wherein the infrared inspection station comprises two sets of infrared emitters and detectors arranged on opposite sides of the transport path so as to view opposite sides of the documents.
 16. Apparatus according to claim 15, wherein the sets of infrared emitters and detectors are offset from one another in the transport direction.
 17. Apparatus according to claim 14, wherein the or each array is arranged opposite a black reference surface.
 18. Apparatus according to claim 14, wherein the transport system includes a diverter operable by the control system to divert documents to one of a number of output locations in accordance with the determined identity. 